Apparatus and method for spinning pipe

ABSTRACT

A pipe spinner and method for spinning pipe used in oil wells. The pipe is engaged simultaneously by a chain and by frictiondrive rollers. Both the chain and the rollers are driven. The beneficial results thus achieved include increased torque, and greatly extended chain life. The chain is a silent chain, and has an inverse internal portion which mounts around the pipe without any necessity for latching of jaws or for breaking of the chain. Tightening of the chain is effected by power cylinders which close the jaws on which are mounted (a) sprockets for the chain, and (b) the friction-drive rollers associated with such sprockets.

[ Sept. 23, 1975 APPARATUS AND METHOD FOR SPINNING PIPE [75] Inventor:Ernest D. Hauk, Signal Hill, Calif.

[73] Assignee: Spinnerhawk Company, Signal Hill,

Calif.

[22] Filed: Aug. 24, 1973 [21] Appl. No.: 391,295

Related US. Application Data [63] Continuation-impart of Ser. No.238,069, March 27,

[52] US. Cl. 81/57.l7; 81/57.34; 166/78; 173/164 [51] Int. Cl. B25Bl7/00; B25B 13/50 [58] Field of Search..'. 8l/57.15, 57.16, 57.17,

2.353.642 7/1944 Buice 81/57.]7 2,523,159 9/1950 Stone... 8l/57.172,784,626 3/1957 Paget 8l/57.l7

Primary Examiner-Al Lawrence Smith Assistant Examiner-James G. SmithAttorney, Agent, or FirmGausewitz, Carr & Rothenberg [5 7] ABSTRACT Apipe spinner and method for spinning pipe used in oil wells. The pipe isengaged simultaneously by a chain and by friction-drive rollers. Boththe chain and the rollers are driven. The beneficial results thusachieved include increased torque, and greatly extended chain life. Thechain is a silent chain, and has an inverse internal portion whichmounts around the pipe without any necessity for latching of jaws or forbreaking of the chain. Tightening of the chain is effected by powercylinders which close the jaws on which are mounted (a) sprockets forthe chain, and (b) the friction-drive rollers associated with suchsprockets.

21 Claims, 7 Drawing Figures US Patent Sept. 23,1975 Sheet 1 0M USPatent Sept. 23,1975 Sheet 2 of4 3,906,820

US Patent Sept. 23,1975 Sheet 3 01 4 3,906,820

US Patent Sept. 23,1975 Sheet 4 of4 3,906,820

APPARATUS AND METHOD FOR SPINNING PIPE CROSS-REFERENCE TO RELATEDAPPLICATION This application is a continuation-in-part of my copendingpatent application Ser. No. 238,069, filed Mar. 27, 1972, forPipe-Spinning Apparatus and Method.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to the field of apparatus and methods for rotating substantiallycylindrical objects, particularly drill pipe, drill collars, casing,etc. The word cylindricaF is employed in this specification in itsordinary or common sense, namely to define objects which have a circularor substantially circular exterior cross-sectional shape.

2. Description of Prior Art The cited copending application sets forthmuch background, and specifies much prior art, all relating to thelong-standing effort to replace the dangerous and unsatisfactoryspinning chain. The cited application also describes and claims anapparatus and method which are greatly superior to those of the priorart. In the present application, there are described and claimed anapparatus and method which have the same superiorities over the priorart and, in addition, are characterized by an even greater drivingtorque and by a much extended chain life.

There are large numbers of prior-art pipe-spinner devices wherein thepipe is engaged and driven by a chain (or other flexible drive element)only, or by frictiondrive rollers only. There is no such device known toapplicant wherein both a chain (or other flexible driveelement) andfriction-drive rollers simultaneously engage and drive the pipe. Suchsimultaneous use of the chain and of friction-drive rollers achieves thesurprising benefit of increasing the drive torque, as well as increasinggreatly the chain life. The torque increase and the life increase occurwithout losing any of numerous benefits of chain-type devices overdevices which have rollers only.

In order to be highly practical and fast-acting, a pipe spinner shouldoperate from only one side of the pipe. From such one side, the spinnershould grab the pipe, then spin it, then let loose. The apparatusdescribed herein and in the cited copending application are of suchtype, and are to be contrasted with prior art apparatus of types whereinthe chain had to be broken each time the tool was mounted on the pipe,or wherein a latching means had to be closed on the side. of the piperemote from the main portion of the spinning apparatus, or wherein therewere no power-operated jaws, or wherein the pipe was not engageddirectly. Some prior art tools of these last-mentioned types are shown.in the following patents: US. Pat. Nos. 1,760,167; 1,805,007; 1,925,970;2,460,671; and 2,573,212.

SUMMARY OF THE INVENTION The present invention provides pipe-engagingrollers at the ends of power-operated jaws which close toward the pipewith great force. Furthermore, there is provided a chain having aninverse internal portion, the ends of which bend around sprocketslocated at the jaw ends. The diameters of the rollers are sufficientlylarge that they engage the pipe and relieve the loads on the bent chainportions which extend around the indicated sprockets. Such bent portionsare, therefore, not compressed between the sprockets and the pipe,despite the great force of the jaws. Accordingly, the lives of the chainand sprockets are very greatly extended. The chain should be a silentchain, as described and claimed in the cited patent application, toachieve numerous advantages relative to (for example) gripping the pipewithout damaging the same, and relative to achievement of a desirableclutching action when the joint seats.

According to one important aspect of the present invention, the rollersare connected to the sprockets in such manner that the rollers areforcibly and positively driven thereby. The rollers are thusfriction-drive rollers which engage and drive the pipe. The friction between rollers and pipe is great, because of the great closing powercreated in the jaws. The rollers thus engage the pipe and friction-driveit at a plurality of points about the pipe circumference, and the silentchain engages the pipe and friction-drives it at a large number of otherpoints around such circumference. There should be no teeth on eitherrollers or chain, all gripping being instead frictional and resultingfrom the forcible closing of the jaws and from the resulting greattension created in the chain.

Since there is no need to break the chain when the tool is mounted onthe pipe, or to latch the jaws together, the apparatus and method areoperated on only one side of the pipe and are therefore extremelypractical and fast acting. The described combination of power-closedjaws, friction-drive rollers, and silent chain having an inverseinternal portion achieves many advantages. Such advantages include (forexample) high torque, long chain life, great adaptability to fit onpipes of different diameters, ability to grip effectively on oily anddirty pipes, minimized damage to the pipe, and ability to work onsurfaces which are not perfectly cylindrical. Surprisingly, the presenttool with driven rollers creates more torque than the same tool with norollersthis despite the fact that roller-type tools nor mally createless drive torque than do chain-type tools.

BRIEF DESCRIPTIONOF THE DRAWINGS FIG. 1 is an isometric view of thepresent apparatus, 1

said view corresponding substantially to FIG. 1 of the above-citedpatent application, but showing the friction-drive rollers mounted inthe jaws and also showing a different form of suspension;

FIG. 2 is a bottom plan view, corresponding generally to FIG. 4 of thecited application, and showing the present apparatus when in thepipe-gripping position;

FIG. 3 is a vertical sectional view on line 3-3 of FIG. 2 and whichcorresponds generally to FIG. 6 of the cited application;

FIG. 4 is a horizontal sectional view which corresponds generally toFIG. 7 of the cited application, the jaws being shown in an openposition permitting introduction of the pipe;

FIG. 5 is a horizontal section view on line 5-5 of FIG. 3 andcorresponding generally to FIG. 8 of the cited application, the jawsbeing shown closed on the pipe;

FIG. 6 is an enlarged fragmentary vertical sectional view on line 66 ofFIG. 5, and illustrating the drive means between the sprockets and theassociated friction-drive rollers; and

FIG. 7 is an enlarged fragmentary isometric view illustrating a portionof the silent chain.

DESCRIPTION OF THE PREFERRED EMBODIMENT Except as specifically stated inthe present specification, the apparatus and method described herein areidentical to those described in the above-cited patent application Ser.No. 238,069. Said application Ser. No. 238,069 is hereby incorporated byreference herein, as though set forth in full.

To summarize briefly the various basic components of the presentapparatus, an elongated closed-loop flexible drive element 33 is somounted that it has an external portion 33a, an inverse internal portion33b, and two return-bent portions 330 which connect the external portionto the internal portion.

The flexible drive element should be a silent chain as described andclaimed in the cited patent application. Such chains are well known inother arts, one example (suitable for use as the flexible drive element33) being given by US. Pat. No. 3,661,025 for a Silent Chain and Methodof Assembly Thereof, which patent is hereby incorporated by referenceherein as though set forth in full.

Silent chain is a recognized term for an invertedtooth chain made up ofa large number of corresponding planar leaf links 36 the ends of whichoverlap each other in alternating relationship as shown in FIG. 7. Eachleaf link has an inner bearing edge 37 adapted to engage the pipe 34,and also has at each end thereof (and on the side opposite edge 37) apair of sprocket teeth 38 which are shaped to mesh with the varioussprocket wheels. The bearing edges 37 of the various links are shown asbeing substantially straight, but they may also be slightly concave inorder to conform more closely to the exterior surface of pipe 34.

In the illustrated silent chain 33, the various leaf links 36 aredisposed in pairs, such as 360 and 36b, which are coextensive, paralleland in surface contact with each other. Large numbers of such pairs aredisposed in what may be termed layers, in the alternating relationshipshown in FIG. 7. Pivot pins 39 extend through the end portions of theleaf links to hold the chain together in pivotal relationship.

The silent chain 33 (and the sprocket wheel teeth) are preferablyconstructed in accordance with American Society of Automotive EngineersStandard 1329.2. Such chain is well known in industry, being desirablefor various purposes because of its silent operation, strength,durability, etc. In accordance with the present apparatus and method,the relatively silent operation of the chain is not a factor, thepurpose being instead to create large bearing areas at the inner leafedges 37 and which engage the external cylindrical surface of the pipe34 to be spun.

When a chain is employed having the indicated leaf edges 37, and thelarge bearing area, it is not necessary to provide teeth on the innersurfaces of the chain (the pipe-engaging surfaces thereof), so thatthere is a minimum possibility of damage to the pipe. Furthermore, whenno pipe-engaging teeth are employed, the chain may more readily sliprelative to the pipe when the joint bottoms out.

The use of the silent chain in combination with the very largejaw-closing pressures indicated below, permit the spinning apparatus tocreate a sufficient torque to spin large pipes at high speed, despitethe presence of water, oil, etc., on. the pipe. One advantage of thesilent chain is that it is substantially incapable of being stretched.Furthermore. it is a primary advantage that the pipe is spun without anysubstantial damage thereto.

The chain 33 extends around sprocket wheels 24 which are fixedly mountedat the front end of the main housing of the apparatus (such housingconstituting a support for various components of the apparatus).Pivotally connected to the main housing at the axes of sprocket wheels24 are thejaws 16a and 17a, such jaws respectively corresponding to jaws16-17 of the cited application except as specified hereinafter. The jawshave sprocket wheels (described below) at the outer ends thereof andaround which the chain 33 bends at the return-bent portions 336.

When jaws l6a-17a are in the opened condition of FIGS. 1 and 4, theapparatus may be mounted around a vertical pipe 34 to be spun. Then, thejaws are closed with much force, for example to the position of FIGS. 2and 5, thereby creating a large amount of tension in the inverseinternal portion 33b to cause such portion to frictionally engage theexterior pipe surface with great bearing pressure. The inverse internalportion engages the exterior pipe surface about a majority of thecircumference thereof but not about the full circumference. When thejaws are thus in closed condition, they maintain the pipe in position inthe inverse internal portion of the chain.

Opening and closing of jaws 16al7a is effected by power means best shownin FIGS. 2 and 3, namely, pneumatic cylinders 61 the pistons of whichconnect to the jaws through cranks and linkages as described in detailin the cited application. The cranks and linkages include crank arms 56which are fixedly associated with the jaws 16a17a.

When the jaws are closed, the distal ends thereof do not touch eachother (and thus act as mutual stops). Instead, the chain 33 acts as thesole means to limit the degree of jaw closing, the result being thatclosing of the jaws creates much tension in the chain. The jaws are soconstructed that, if there were no chain, the jaw ends would (when thejaws are closed) touch each other.

After the jaws are closed to grip the chain portion 33b on pipe 34, thechain is driven in order to effect rapid spinning of the pipe. Suchdriving is effected by a pneumatic motor 42 which operates through agear box 47 to rotate a shaft 51 (FIGS. 3 and 4) on which is mounted thedrive sprocket 32 for chain 33. Thus, when a control valve is operatedto admit air into the motor 42, the shaft 51 is driven to thus drive thesprocket wheels 32 and thereby drive chain 33 to rotate pipe 34.

The motor 42 and gear box 47 are movable toward and away from the pipe34, thus moving the axis of shaft 51 and of sprocket wheel 32. Suchmovement is not effected except when it is desired to adapt theapparatus for driving a substantially different diameter of pipe 34. Toachieve the indicated adjustment, a chain guide and lock element 41 areshifted in response to ro tation of an adjustment screw 52. After theadjustment is completed, lock screws 48 (which extend through a flangeportion of the gear box 47, and are threaded into element 41) aretightened in order to lock element 41 (and thus elements 42, 47 and 51)in position. In order that the described adjustment may occur, the upperportion of the housing of the apparatus is suitably slotted, asillustrated, to receive the lock screws.

The apparatus is suspended, adjacent the wellhead of an oil well, bymeans of an inverted V-shaped suspension bar 110 the lower ends of whichconnect to the housing of the apparatus. At the upper or apex portion ofbar 110 is provided a mounting means 111 by which the bar may beconnected to the lower link of a suspension chain 112. The mountingmeans 111 is so constructed that the chain may be connected at differentaxial points therealong, thus permitting balancing of the spinningapparatus in generally a horizontal condition.

In order to facilitate manipulation of the apparatus, suitable handles113 are provided below each jaw 16a-17a as illustrated (relative to jaw16a) in FIG. 1.

DETAILED DESCRIPTION OF THE FRICTIONDRIVE ROLLERS AND ASSOCIATEDSPROCKET WHEELS As best shown in FIGS. 3 and 6, each jaw 16a-17a isenlarged at the outer portion thereof in order that it may incorporatetwo friction-drive rollers 116 and one sprocket wheel 117. Since theelements at the outer ends of the two jaws 16a-l7a are identical, onlythe elements incorporated in jaw 16a are shown and described in detail.

Referring to FIG. 6, the two rollers 116 are disposed on opposite sidesof (above and below) the sprocket wheel 117, all of the elements 116 and117 being mounted coaxially of each other on a vertical shaft. Morespecifically, such shaft is illustrated as being bolt 118 which extendsthrough collars 119 welded on the upper and lower walls of the housingportion of jaw 16a, there being nuts 121 provided to maintain bolt 118fixedly inposition. Mounted around bolt 118, between the upper and lowerhousing walls of the jaw, is a sleeve 122 around which are provided aplurality of sets of antifriction bearings (for example, needlebearings) 123. The rollers 116 and sprocket wheel 117 are mounted inencompassing relationship to such bearings 123 in order that suchelements 116-117 will rotate freely relative to the shaft or bolt 118.

Sprocket wheel 117 (and the other sprocket wheels) is of the typeconventionally employed with a silent chain, having vertical teeth whichmesh with the tooth portions of the chain 33 as described in the citedpatent application and also in said US. Pat. No. 3,661,025. Eachsprocket wheel may be termed a silent chain" sprocket wheel.

It is pointed out that the teeth of the silent chain do not engage thepipe 34, engagement instead being effected at a multiplicity ofuntoothed bearing edges as described above. As is known and conventionalin many silent chains, guiding of the chain is effected by means ofguide links which pass through a circumferentially grooved centralregion of the sprocket wheel 117. Such guide links are indicated at 124in FIG. 6, and are extended through the circumferential groove 126 inwheel 117. The other sprockets of the apparatus have similarcircumferential grooves for reception of the guide links 124.

As shown in FIG. 6, the cylindrical peripheral surfaces of rollers 116are in direct bearing engagement with the exterior cylindrical surfaceof pipe 34. Such rollers 116 have diameters sufficiently great to insurethat neither the chain nor the sprocket wheels will be damaged due tothe pressure engagement with the pipe 34. Stated more specifically, theroller diameters are sufficient that the return-bent portions 33c ofchain 33 will not be crushed or compressed between sprocket wheels 117and the exterior pipe surface. It has been found that, if such crushingor compression is permitted to occur, it results in brinelling of thechain links and/or of the sprocket wheels, with consequent stiffening ofthe chain and reduction in chain life.

As an example, in the illustrated embodiment, a small gap (for example,0.030 inch) is provided at 127 (FIG. 6) between each return-bent chainportion 330 and the exterior pipe surface. The presence of such gapassures that even substantial wearing on the rollers, so as to reducethe diameters thereof, will not cause the chain 33 to be compressedbetween sprocket wheels 117 and the pipe to thereby cause wear andstiffening of the chain.

It is emphasized that each gap 127 is only present at a relatively smallregion immediately between sprocket wheel 117 and the pipe, and that thechain portion 33b is in direct engagement with a major portion of thecircumference of the pipe. Thus, there are two important areas offrictional engagement between the drive elements and the pipe 34. One ofsuch areas is at the rollers 116, and the other of such areas (which ismuch larger than the first) is along a major portion of thecircumference of the pipe and at which the silent chain frictionallyengages the pipe.

Stated in another manner, the chain frictionally engages the pipe alonga long are of the circumference thereof, whereas the friction-driverollers frictionally engage the pipe at about (or between) the ends ofsuch long arc. The word circumference is presently employed to denoteonly one circumferential region along the length of the pipe.

Applicant has discovered that, if the rollers 116 are not driven butinstead are permitted to rotate freely in the manner of antifrictionbearings for the pipe 34, then the amount of drive torque created by thespinning apparatus is drastically reduced. If, on the other hand, therollers are positively driven with or by the sprockets 117, then thedrive torque created by the present spinning apparatus is increased incomparison to the torque which would be created if no rollers wereemployed. Such an increase was not to be expected, particularly becausethe rollers are only in line contact with the pipe whereas the chainportion (which was lifted, by the rollers, off the pipe) was in surfacecontact with the pipe.

To summarize, therefore, the presence of the driven rollers 116 createstwo major benefits relative to'the construction described in the citedapplication, wherein no such rollers are employed. These benefits areincreased drive torque and greatly increased chain life.

The driving of the rollers 116 on each jaw l6a-17a is effected by meansof drive pins 128 which extend into registered apertures in the ends ofthe sprocket and of the rollers. Since each sprocket 117 is driven bythe chain 33 (which chain is in turn driven by the drive sprocket wheel32 in response to operation of motor 42 and gear box 47), and since therollers 116 are connected to the sprocket 117 by means of drive pins128, it follows that the rollers 116 are driven positively, and operateas friction-drive rollers for the pipe 34.

DESCRIPTION OF THE METHOD The jaws l6a17a are first opened by operationof the pneumatic cylinders 61, for example to the position shown inFIGS. 1 and 4. The amount of opening is enough to permit the apparatusto be swung toward the pipe 34 so that the pipe enters the space betweenthe return bent portions 330 of the chain and becomes largely surroundedby the inverse internal portion 33b thereof.

The cylinders 61 are then operated to close the jaws l6a-l7a, with greatforce, for example to the positions shown in FIGS. 2 and 5. The jaws donot close to positions such that they engage each other and serve asmutual stops, the degree of closing being instead determined by thelength of the chain. Thus, the jaws close until the chain tension is sogreat that it counterbalances the jaw-closing force. The described jawclosing and chain tension cause strong pressure engagement between therollers 116 of the pipe, and between the inverse internal chain portion33b and the pipe. Such pressure engagements create great friction,without damaging the pipe, which friction is operative to spin the pipeafter the motor 42 is started to drive (by means of gear box 47) theshaft 51 and thus the drive sprocket wheel 32 and chain 33.

Driving is effected until the desired joint is either made or broken, atone end of the pipe 34, following which the cylinders 61 are operated toopen the jaws and permit the operation to be repeated with a differentlength of pipe.

As described in detail above, the driving of the chain effects drivingof the rollers 116 so that they operate as friction-drive rollers andcooperate with the inverse internal chain portion 33b in driving andspinning the pipe without damage thereto.

The apparatus may operate on pipes of slightly different diameters,without effecting any adjustment in the position of the drive sprocketwheel 32. When a pipe of substantially different diameter is to bedriven, the position of the axis of wheel 32 is adjusted as describedheretofore and in the cited application. Briefly, this adjustment iseffected by loosening the lock screws 48, turning the adjustment screw52 until the position of the shaft 51 is such that the chain is adjustedto the desired length, and then re-tightening the screws 48. The methodis then repeated in the manner described above but with the pipe ofsubstantially different diameter.

If desired, very high torques may be created with the present apparatus,particularly if the silent chain is caused to be very wide and if thereis a very large gear reduction between the pneumatic motor 42 and thedrive sprocket wheel 32. It is also pointed out that the pneumatic motor42 could be replaced by hydraulic means in order to increase torquecapabilities.

The foregoing detailed description is to be clearly understood as givenby way of illustration and example only, the spirit and scope of thisinvention being limited solely by the appended claims.

I claim:

1. Apparatus for spinning pipe, which comprises:

a. a support,

b. first and second jaws movably mounted on said support,

0. power means to close saidjaws with a large amount of force,

d. an elongated closed-loop flexible drive element,

said flexible dri e element having an external portion and an inverseinternal portion disposed within said external portion,

said inverse internal portion being adapted to receive and engage thepipe to be spun, e. first and second wheels mounted, respectively, on

said jaws,

said wheels having extended therearound the return-bent portions atwhich said external portion of said flexible drive element connects tosaid internal portion thereof,

f. roller means mounted on said jaws to engage the pipe in response toforcible closing of said jaws by said power means, and to prevent saidflexible drive element or said wheels from being damaged or worn due toforcible engagement with said pipe in the vicinity of said wheels; and

. means to drive said flexible drive element, and thus effect spinningof said pipe, after said jaws have been closed by said power means, saiddrive means also being connected to effect driving of said roller meansin such direction that said roller means serve as drive elements foraiding said flexible drive element in spinning said said driving of saidroller means being such that said roller means impart driving torque tosaid pipe through the regions of engagement between said roller meansand said pipe.

2. The invention as claimed in claim 1, in which said power meanscomprise cylinder means and associated piston means, and also comprisemeans to introduce pressurized fluid into said cylinder means.

3. The invention as claimed in claim 1, in which said flexible driveelement is a chain, and in which said wheels are sprocket wheels meshedwith said chain.

4. The invention as claimed in claim 3, in which said chain is a silentchain, in which said sprocket wheels are shaped to mesh with the teethof said silent chain, in which the untoothed bearing edges of said chainare on the interior side of said inverse internal portion so that saidbearing edges will engage the exterior cylindrical surface of said pipewhen said jaws are closed, and in which said roller means prevent saidchain from being compressed between said pipe and said wheels.

5. The invention as claimed in claim 1, in which said flexible driveelement has such length that it prevents said jaws from closing intoengagement with each other, said flexible drive element constitutingwhen said pipe is disposed in said inverse internal portion the solemeans for counterbalancing the force exerted by said power means,whereby said inverse internal portion is tensioned greatly and thereforebears with great force against said pipe. 4

6. The invention as claimed in claim 1, in which said flexible driveelement is a chain comprising a large number of planar leaf links theends of which overlap each other in alternating relationship, saidoverlapped ends being pivotally connected to each other by pivot pins,each of said leaf links having at one side thereof an untoothed bearingedge disposed at said inverse internal portion and adapted to forciblyengage the exterior surface of said pipe without damaging the same, atleast some of said links incorporating protuberances on the side thereofopposite said untoothed bearing edges, said protuberances forming partof said drive means recited in clause (g).

7. The invention as claimed in claim 1, in which said jaws are pivotallymounted on said support, and in which said jaws are devoid of any latchmeans for connecting said jaws to each other on the side of said piperemote from said support.

8. The invention as claimed in claim I, in which said roller meanscomprise rollers mounted on said first jaw in axial alignment with saidfirst wheel, in which said roller means further comprise rollers mountedon said second jaw in axial alignment with said second wheel, and inwhich the diameters of said rollers are sufficiently large that saidrollers engage said pipe when said jaws are closed and therefore relievethe pressures tending to damage said flexible drive element or saidwheels.

9. The invention as claimed in claim 8, in which said diameters of saidrollers are sufficiently large that said flexible drive element is, atthe portion thereof adjacent said wheels, spaced away from said pipe.

10. The invention as claimed in claim 8, in which said rollers areconnected to said wheels and therefore rotate therewith, whereby saidrollers serve as drive rollers for aiding said flexible drive element inspinning said pipe.

11. The invention as claimed in claim 1, in which said means to drivesaid flexible drive element comprises a power-driven wheel drivinglyengaged with said flexible drive element, and means to mount said powerdriven wheel in such manner that the axis thereof is fixed in positionat all times when the apparatus is being employed to spin pipe having afixed predetermined diameter.

12. Apparatus for rotating pipe about the longitudinal axis thereof,which comprises:

a. an elongated flexible drive element adapted to engage a pipe along asubstantial arc of the exterior surface thereof, to thereby rotate thepipe about the longitudinal axis thereof, said flexible drive elementbeing a closed loop having an external portion and an inverse internalportion,

the interior surface of said inverse portion engaging the exteriorsurface of said pipe around a major portion of the pipe circumference,

b. drive roller means adapted to engage said pipe to rotate the sameabout the longitudinal axis thereof, said flexible drive element andsaid drive roller means engaging said pipe simultaneously with eachother, said drive roller means engaging said pipe adjacent thereturn-bent portions at which said external portion of said flexibledrive element connects to said inverse internal portion thereof, saidreturn-bent portions being mounted around wheels, said roller meanscomprising rollers drivingly related to said wheels for driving thereby,and

. means to forcibly drive said flexible drive element and said rollersto thus effect rotation of said pipe about the longitudinal axis thereofdue to the conjoint operation of said flexible drive element and saidrollers,

said drive means being such that said flexible drive element impartsdriving torque to said pipe through the arc of engagement between saidflexible drive element and said exterior surface, said drive means alsobeing such that said rollers imrespectively part driving torque to saidpipe through the regions of engagement between said rollers and saidexterior surface.

13. The invention as claimed in claim 12, in which said rollers arecoaxial with said wheels and are rigidly connected thereto for conjointrotational movement.

14. The invention as claimed in claim 13, in which the diameters of saidrollers are sufficiently large to prevent damage to said flexible driveelement or said wheels due to forcible engagement with said pipe.

15. The invention as claimed in claim 12, in which said flexible driveelement is a silent chain.

16. A pipe-spinning apparatus for spinning pipe at the wellheads of oilwells, which comprises:

a. a movable support,

b. first and second jaws pivotally mounted on said support for pivotalmovement in such manner that the distal ends of said jaws move towardand away from each other as said jaws close and open, said distal endsbeing so related to each other that,

unless restrained, they would touch upon closing movement of said jaws,c. piston and cylinder means connected to said jaws to forcibly closethe same and thereafter open them, d. first and second silent-chainsprocket wheels rotatably mounted, respectively, at end portions of saidfirst and second jaws, e. a silent chain having an external portion andan inverse intemal portion, said external and internal portionsconnecting to each other at return-bent portions which bend around andmesh with said first and second sprocket wheels,

said internal, portion being adapted to receive the pipe to be spun,

f. a drive sprocket wheel mounted on said movable support and meshedwith said chain, the length of said chain being such that when saidinverse chain portion encompasses a pipe of predetermined diameter saidjaws may not be closed sufficiently far to cause said distal endsthereof to touch each other,

g. means mounted on said support to drive said drive sprocket wheel,

h. first and second roller means respectively mounted at said endportions of said first and second jaws,

said first and second roller means being respectively coaxial with saidfirst and second sprocket wheels,

said roller means having diameters sufficiently large to prevent saidreturn-bent chain portions from being compressed between said pipe andsaid first and second sprocket wheels, and

i. means provided to drivingly connect in positive manner said firstroller means to said first sprocket wheel, and said second roller meansto said second sprocket wheel,

whereby said roller means constitute friction-drive rollers whichcooperate with said inverse internal portion in spinning said pipe.

17. The invention as claimed in claim 16, in which means are provided toadjust the position of the axis of said drive sprocket wheel, and tolock said axis in adjusted position, whereby to adapt the apparatus forspinning pipes of different diameters.

18. The invention as claimed in claim 16, in which additional sprocketwheels for said silent chain are respectively mounted at the pivot axesof said first and second jaws, said additional sprocket wheels beingmeshed with said chain.

19. A method of rotating pipe adjacent the wellhead of an oil well, tothereby make or break threaded joints between coaxial pipe sections,which comprises:

a. wrapping a section of a flexible drive element around at least amajor portion of the circumference of said pipe to be rotated, and inengagement with the exterior surface of said pipe, b. engaging rollermeans with said exterior surface of said pipe in the general region ofsaid flexible drive element, 0. creating great tension in said flexibledrive element to force it into pressure engagement with said exteriorsurface, d. creating large bearing pressure between said roller meansand said exterior surface, and e. simultaneously driving both saidflexible drive element and said roller means to thereby rotate saidpipe, said driving of said flexible drive element imparting drivingtorque to said pipe through the area of engagement between said flexibledrive element and said exterior pipe surface,

said driving of said roller means imparting driving torque to said pipethrough the area of engagement between said roller means and saidexterior pipe surface.

20. Apparatus for rotating about the longitudinal axis thereof a pipewhich has a substantially cylindrical exterior surface, which apparatuscomprises:

a. a support, b. first and second jaws mounted on said support andmovable between an open position in which said first and second jaws arerelatively remote from each other and a closed position in which saidfirst and second jaws are relatively close to each other, e. anelongated closed-loop flexible chain,

said chain comprising a large number of planar leaf links the ends ofwhich overlap each other in alternating relationship, and pivot pinspivotally connecting said overlapped ends together, said leaf linksbeing in a relatively high density such that there is a close spacingbetween adjacent links at the central portions thereof intermediateadjacent ones of said pivot pins,

said leaf links having on one side thereof untoothed bearing edgeportions adapted to forcibly engage the substantially cylindricalexterior surface of the pipe without damaging the same, and havingprotuberance means on the other side thereof, d. wheel means comprisinga plurality of wheels including first and second wheels mounted,respectively, on said first and second jaws, said chain being mountedaround said wheel means in such manner that, when said jaws are in saidclosed position, there is an external chain section, an inverse internalchain section disposed within said external section, and junctionregions between said external and internal chain sections return-bentand extending respectively around said first and second wheels,

said internal chain section being adapted to receive said pipe andbeingso oriented that said untoothed bearing edge portions of said leaf linksin said internal chain section engage said substantially cylindricalexterior surface of said pipe,

said internal chain section engaging, when said jaws are in said closedposition, said substantially cylindrical exterior surface of said pipeabout a majority of the circumference thereof but not about the fullcircumference,

e. rollers mounted on said jaws to engage said substantially cylindricalexterior surface of said pipe adjacent said junction regions, saidrollers having peripheral surfaces which are closer to said exteriorpipe surface than are said leaf links and said first and second wheelsso that said rollers engage said exterior pipe surface and prevent saidleaf links and said first and second wheels from being damaged or worndue to forcible compression of said leaf links between said exteriorpipe surface and said first and second wheels,

f. power means selectively operable for moving said jaws to said openposition thereof and for moving said jaws to said closed positionthereof, such that said internal chain section so engages saidsubstantially cylindrical surface of said pipe, and for causing a largetension to be created in said chain, thereby causing said untoothedbearing edge portions of said leaf links in said internal chain sectionto engage with great force said substantially cylindrical exteriorsurface of said pipe so received, said jaws operating, when in saidclosed position, to

hold said pipe in position in said internal chain section, and

g. means to drive said chain, and thus effect rotation of said pipeabout the longitudinal axis thereof, when said jaws are in said closedposition and said chain has thus been tensioned, said means to drivesaid chain including at least one of the wheels in said wheel means,

said one wheel incorporating protuberance means meshing with saidprotuberance means of said leaf links on said other side of said leaflinks,

said means to drive said chain further including power means forrotating said one wheel for causing said protuberance means thereof toreact with said protuberance means of said leaf links on said other sideof said leaf links and thus advance said chain,

21. A method of rotating cylindrical pipe sections adjacent the wellheadof an oil well, to thereby make or break threaded joints between coaxialpipe sections, which method comprises:

a. providing a closed-loop flexible drive chain comprising a largenumber of planar alternated leaf links the ends of which are pivotallyconnected to each other by pivot pins, such leaf links having at oneside thereof untoothed bearing edge portions adapted to forcibly engagethe pipe surface without damaging the same, and having at the other sidethereof protuberance means adapted to be engaged by a driving means,

b. then causing said chain to assume a shape in which it has an externalsection, an inverse internal section disposed within said externalsection, and bent portions between said external and internal sections,and has said untoothed bearing edge portions of said leaf links on theinner side of said internal e. engaging and moving said protuberancemeans of chain section, said leaf links to thus drive said chain withconsec. disposing a cylindrical pipe section in said internal quentrotation of said pipe section about the longichain section, tudinal axisthereof,

d. causing said chain to engage a majority of the cirsaid step ofengaging and moving said protubercumference of said pipe section, butless than the ance means being performed by causing protuentirecircumference thereof, in such manner that berance means on at least onepower-operated said pipe section is constrained by said internal drivewheel to engage and drive said pr0tuberchain section and prevented frommoving out of ance means on said leaf links, and the same, and creatinggreat tension in said chain f. preventing from forcibly engaging saidpipe section to thereby cause said untoothed bearing edge por said bentportions of said chain which connect said tions of said leaf links insaid internal chain section external chain section and said internalchain secto forcibly engage said pipe section about a majortion. ity ofthe circumference thereof,

1. Apparatus for spinning pipe, which comprises: a. a support, b. firstand second jaws movably mounted on said support, c. power means to closesaid jaws with a large amount of force, d. an elongated closed-loopflexible drive element, said flexible drive element having an externalportion and an inverse internal portion disposed within said externalportion, said inverse internal portion being adapted to receive andengage the pipe to be spun, e. first and second wheels mounted,respectively, on said jaws, said wheels having extended therearound thereturn-bent portions at which said external portion of said flexibledrive element connects to said internal portion thereof, f. roller meansmounted on said jaws to engage the pipe in response to forcible closingof said jaws by said power means, and to prevent said flexible driveelement or said wheels from being damaged or worn due to forcibleengagement with said pipe in the vicinity of said wheels; and g. meansto drive said flexible drive element, and thus effect spinning of saidpipe, after said jaws have been closed by said power means, said drivemeans also being connected to effect driving of said roller means insuch direction that said roller means serve as drive elements for aidingsaid flexible drive element in spinning said pipe, said driving of saidroller means being such that said roller means impart driving torque tosaid pipe through the regions of engagement between said roller meansand said pipe.
 2. The invention as claimed in claim 1, in which saidpower means comprise cylinder means and associated piston means, andalso comprise means to introduce pressurized fluid into said cylindermeans.
 3. The invention as claimed in claim 1, in which said flexibledrive element is a chain, and in which said wheels are sprocket wheelsmeshed with said chain.
 4. The invention as claimed in claim 3, in whichsaid chain is a silent chain, in which said sprocket wheels are shapedto mesh with the teeth of said silent chain, in which the untoothedbearing edges of said chain are on the interior side of said inverseinternal portion so that said bearing edges will engage the exteriorcylindrical surface of said pipe when said jaws are closed, and in whichsaid roller means prevent said chain from being compressed between saidpipe and said wheels.
 5. The invention as claimed in claim 1, in whichsaid flexible drive element has such length that it prevents said jawsfrom closing into engagement with each other, said flexible driveelement constituting when said pipe is disposed in said inverse internalportion the sole means for counterbalancing the force exerted by saidpower means, whereby said inverse internal portion is tensioned greatlyand therefore bears with great force against said pipe.
 6. The inventionas claimed in claim 1, in which said flexible drive element is a chaincomprising a large number of planar leaf links the ends of which overlapeach other in alternating relationship, said overlapped ends beingpivotally connected to each other by pivot pins, each of said leaf linkshaving at one side thereof an untoothed bearing edge disposed at saidinverse internal portion and adapted to forcibly engage the exteRiorsurface of said pipe without damaging the same, at least some of saidlinks incorporating protuberances on the side thereof opposite saiduntoothed bearing edges, said protuberances forming part of said drivemeans recited in clause (g).
 7. The invention as claimed in claim 1, inwhich said jaws are pivotally mounted on said support, and in which saidjaws are devoid of any latch means for connecting said jaws to eachother on the side of said pipe remote from said support.
 8. Theinvention as claimed in claim 1, in which said roller means compriserollers mounted on said first jaw in axial alignment with said firstwheel, in which said roller means further comprise rollers mounted onsaid second jaw in axial alignment with said second wheel, and in whichthe diameters of said rollers are sufficiently large that said rollersengage said pipe when said jaws are closed and therefore relieve thepressures tending to damage said flexible drive element or said wheels.9. The invention as claimed in claim 8, in which said diameters of saidrollers are sufficiently large that said flexible drive element is, atthe portion thereof adjacent said wheels, spaced away from said pipe.10. The invention as claimed in claim 8, in which said rollers areconnected to said wheels and therefore rotate therewith, whereby saidrollers serve as drive rollers for aiding said flexible drive element inspinning said pipe.
 11. The invention as claimed in claim 1, in whichsaid means to drive said flexible drive element comprises a power-drivenwheel drivingly engaged with said flexible drive element, and means tomount said power driven wheel in such manner that the axis thereof isfixed in position at all times when the apparatus is being employed tospin pipe having a fixed predetermined diameter.
 12. Apparatus forrotating pipe about the longitudinal axis thereof, which comprises: a.an elongated flexible drive element adapted to engage a pipe along asubstantial arc of the exterior surface thereof, to thereby rotate thepipe about the longitudinal axis thereof, said flexible drive elementbeing a closed loop having an external portion and an inverse internalportion, the interior surface of said inverse portion engaging theexterior surface of said pipe around a major portion of the pipecircumference, b. drive roller means adapted to engage said pipe torotate the same about the longitudinal axis thereof, said flexible driveelement and said drive roller means engaging said pipe simultaneouslywith each other, said drive roller means engaging said pipe adjacent thereturn-bent portions at which said external portion of said flexibledrive element connects to said inverse internal portion thereof, saidreturn-bent portions being respectively mounted around wheels, saidroller means comprising rollers drivingly related to said wheels fordriving thereby, and c. means to forcibly drive said flexible driveelement and said rollers to thus effect rotation of said pipe about thelongitudinal axis thereof due to the conjoint operation of said flexibledrive element and said rollers, said drive means being such that saidflexible drive element imparts driving torque to said pipe through thearc of engagement between said flexible drive element and said exteriorsurface, said drive means also being such that said rollers impartdriving torque to said pipe through the regions of engagement betweensaid rollers and said exterior surface.
 13. The invention as claimed inclaim 12, in which said rollers are coaxial with said wheels and arerigidly connected thereto for conjoint rotational movement.
 14. Theinvention as claimed in claim 13, in which the diameters of said rollersare sufficiently large to prevent damage to said flexible drive elementor said wheels due to forcible engagement with said pipe.
 15. Theinvention as claimed in claim 12, in which said flexible drive elementis a silent chain.
 16. A pipe-spinning apparatus for spinning pipe atthe wellheads of oil wells, which comprises: a. a movable support, b.first and second jaws pivotally mounted on said support for pivotalmovement in such manner that the distal ends of said jaws move towardand away from each other as said jaws close and open, said distal endsbeing so related to each other that, unless restrained, they would touchupon closing movement of said jaws, c. piston and cylinder meansconnected to said jaws to forcibly close the same and thereafter openthem, d. first and second ''''silent-chain'''' sprocket wheels rotatablymounted, respectively, at end portions of said first and second jaws, e.a silent chain having an external portion and an inverse internalportion, said external and internal portions connecting to each other atreturn-bent portions which bend around and mesh with said first andsecond sprocket wheels, said internal portion being adapted to receivethe pipe to be spun, f. a drive sprocket wheel mounted on said movablesupport and meshed with said chain, the length of said chain being suchthat when said inverse chain portion encompasses a pipe of predetermineddiameter said jaws may not be closed sufficiently far to cause saiddistal ends thereof to touch each other, g. means mounted on saidsupport to drive said drive sprocket wheel, h. first and second rollermeans respectively mounted at said end portions of said first and secondjaws, said first and second roller means being respectively coaxial withsaid first and second sprocket wheels, said roller means havingdiameters sufficiently large to prevent said return-bent chain portionsfrom being compressed between said pipe and said first and secondsprocket wheels, and i. means provided to drivingly connect in positivemanner said first roller means to said first sprocket wheel, and saidsecond roller means to said second sprocket wheel, whereby said rollermeans constitute friction-drive rollers which cooperate with saidinverse internal portion in spinning said pipe.
 17. The invention asclaimed in claim 16, in which means are provided to adjust the positionof the axis of said drive sprocket wheel, and to lock said axis inadjusted position, whereby to adapt the apparatus for spinning pipes ofdifferent diameters.
 18. The invention as claimed in claim 16, in whichadditional sprocket wheels for said silent chain are respectivelymounted at the pivot axes of said first and second jaws, said additionalsprocket wheels being meshed with said chain.
 19. A method of rotatingpipe adjacent the wellhead of an oil well, to thereby make or breakthreaded joints between coaxial pipe sections, which comprises: a.wrapping a section of a flexible drive element around at least a majorportion of the circumference of said pipe to be rotated, and inengagement with the exterior surface of said pipe, b. engaging rollermeans with said exterior surface of said pipe in the general region ofsaid flexible drive element, c. creating great tension in said flexibledrive element to force it into pressure engagement with said exteriorsurface, d. creating large bearing pressure between said roller meansand said exterior surface, and e. simultaneously driving both saidflexible drive element and said roller means to thereby rotate saidpipe, said driving of said flexible drive element imparting drivingtorque to said pipe through the area of engagement between said flexibledrive element and said exterior pipe surface, said driving of saidroller means imparting driving torque to said pipe through the area ofengagement between said roller means and said exterior pipe surface. 20.Apparatus for rotating about the longitudinal axis thereof a pipe whichhas a substantially cylindrical exterior surface, which apparatuscomprises: a. a support, b. first and second jaws mounted on saidsupport anD movable between an open position in which said first andsecond jaws are relatively remote from each other and a closed positionin which said first and second jaws are relatively close to each other,c. an elongated closed-loop flexible chain, said chain comprising alarge number of planar leaf links the ends of which overlap each otherin alternating relationship, and pivot pins pivotally connecting saidoverlapped ends together, said leaf links being in a relatively highdensity such that there is a close spacing between adjacent links at thecentral portions thereof intermediate adjacent ones of said pivot pins,said leaf links having on one side thereof untoothed bearing edgeportions adapted to forcibly engage the substantially cylindricalexterior surface of the pipe without damaging the same, and havingprotuberance means on the other side thereof, d. wheel means comprisinga plurality of wheels including first and second wheels mounted,respectively, on said first and second jaws, said chain being mountedaround said wheel means in such manner that, when said jaws are in saidclosed position, there is an external chain section, an inverse internalchain section disposed within said external section, and junctionregions between said external and internal chain sections return-bentand extending respectively around said first and second wheels, saidinternal chain section being adapted to receive said pipe and being sooriented that said untoothed bearing edge portions of said leaf links insaid internal chain section engage said substantially cylindricalexterior surface of said pipe, said internal chain section engaging,when said jaws are in said closed position, said substantiallycylindrical exterior surface of said pipe about a majority of thecircumference thereof but not about the full circumference, e. rollersmounted on said jaws to engage said substantially cylindrical exteriorsurface of said pipe adjacent said junction regions, said rollers havingperipheral surfaces which are closer to said exterior pipe surface thanare said leaf links and said first and second wheels so that saidrollers engage said exterior pipe surface and prevent said leaf linksand said first and second wheels from being damaged or worn due toforcible compression of said leaf links between said exterior pipesurface and said first and second wheels, f. power means selectivelyoperable for moving said jaws to said open position thereof and formoving said jaws to said closed position thereof, such that saidinternal chain section so engages said substantially cylindrical surfaceof said pipe, and for causing a large tension to be created in saidchain, thereby causing said untoothed bearing edge portions of said leaflinks in said internal chain section to engage with great force saidsubstantially cylindrical exterior surface of said pipe so received,said jaws operating, when in said closed position, to hold said pipe inposition in said internal chain section, and g. means to drive saidchain, and thus effect rotation of said pipe about the longitudinal axisthereof, when said jaws are in said closed position and said chain hasthus been tensioned, said means to drive said chain including at leastone of the wheels in said wheel means, said one wheel incorporatingprotuberance means meshing with said protuberance means of said leaflinks on said other side of said leaf links, said means to drive saidchain further including power means for rotating said one wheel forcausing said protuberance means thereof to react with said protuberancemeans of said leaf links on said other side of said leaf links and thusadvance said chain.
 21. A method of rotating cylindrical pipe sectionsadjacent the wellhead of an oil well, to thereby make or break threadedjoints between coaxial pipe sections, which method comprises: a.providing a closed-loop flexible drive chain comprising a large numberof planar alTernated leaf links the ends of which are pivotallyconnected to each other by pivot pins, such leaf links having at oneside thereof untoothed bearing edge portions adapted to forcibly engagethe pipe surface without damaging the same, and having at the other sidethereof protuberance means adapted to be engaged by a driving means, b.then causing said chain to assume a shape in which it has an externalsection, an inverse internal section disposed within said externalsection, and bent portions between said external and internal sections,and has said untoothed bearing edge portions of said leaf links on theinner side of said internal chain section, c. disposing a cylindricalpipe section in said internal chain section, d. causing said chain toengage a majority of the circumference of said pipe section, but lessthan the entire circumference thereof, in such manner that said pipesection is constrained by said internal chain section and prevented frommoving out of the same, and creating great tension in said chain tothereby cause said untoothed bearing edge portions of said leaf links insaid internal chain section to forcibly engage said pipe section about amajority of the circumference thereof, e. engaging and moving saidprotuberance means of said leaf links to thus drive said chain withconsequent rotation of said pipe section about the longitudinal axisthereof, said step of engaging and moving said protuberance means beingperformed by causing protuberance means on at least one power-operateddrive wheel to engage and drive said protuberance means on said leaflinks, and f. preventing from forcibly engaging said pipe section saidbent portions of said chain which connect said external chain sectionand said internal chain section.